text: // SPDX-License-Identifier: GPL-2.0+
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/string.h>
  
  #include "../tools/testing/selftests/kselftest_module.h"
  
  /*
   * Kernel module for testing 'strscpy' family of functions.
   */
  
  KSTM_MODULE_GLOBALS();
  
  /*
   * tc() - Run a specific test case.
   * @src: Source string, argument to strscpy_pad()
   * @count: Size of destination buffer, argument to strscpy_pad()
   * @expected: Expected return value from call to strscpy_pad()
   * @terminator: 1 if there should be a terminating null byte 0 otherwise.
   * @chars: Number of characters from the src string expected to be
   *         written to the dst buffer.
   * @pad: Number of pad characters expected (in the tail of dst buffer).
   *       (@pad does not include the null terminator byte.)
   *
   * Calls strscpy_pad() and verifies the return value and state of the
   * destination buffer after the call returns.
   */
  static int __init tc(char *src, int count, int expected,
  		     int chars, int terminator, int pad)
  {
  	int nr_bytes_poison;
  	int max_expected;
  	int max_count;
  	int written;
  	char buf[6];
  	int index, i;
  	const char POISON = 'z';
  
  	total_tests++;
  
  	if (!src) {
  		pr_err("null source string not supported\n");
  		return -1;
  	}
  
  	memset(buf, POISON, sizeof(buf));
  	/* Future proofing test suite, validate args */
  	max_count = sizeof(buf) - 2; /* Space for null and to verify overflow */
  	max_expected = count - 1;    /* Space for the null */
  	if (count > max_count) {
  		pr_err("count (%d) is too big (%d) ... aborting", count, max_count);
  		return -1;
  	}
  	if (expected > max_expected) {
  		pr_warn("expected (%d) is bigger than can possibly be returned (%d)",
  			expected, max_expected);
  	}
  
  	written = strscpy_pad(buf, src, count);
  	if ((written) != (expected)) {
  		pr_err("%d != %d (written, expected)\n", written, expected);
  		goto fail;
  	}
  
  	if (count && written == -E2BIG) {
  		if (strncmp(buf, src, count - 1) != 0) {
  			pr_err("buffer state invalid for -E2BIG\n");
  			goto fail;
  		}
  		if (buf[count - 1] != '\0') {
  			pr_err("too big string is not null terminated correctly\n");
  			goto fail;
  		}
  	}
  
  	for (i = 0; i < chars; i++) {
  		if (buf[i] != src[i]) {
  			pr_err("buf[i]==%c != src[i]==%c\n", buf[i], src[i]);
  			goto fail;
  		}
  	}
  
  	if (terminator) {
  		if (buf[count - 1] != '\0') {
  			pr_err("string is not null terminated correctly\n");
  			goto fail;
  		}
  	}
  
  	for (i = 0; i < pad; i++) {
  		index = chars + terminator + i;
  		if (buf[index] != '\0') {
  			pr_err("padding missing at index: %d\n", i);
  			goto fail;
  		}
  	}
  
  	nr_bytes_poison = sizeof(buf) - chars - terminator - pad;
  	for (i = 0; i < nr_bytes_poison; i++) {
  		index = sizeof(buf) - 1 - i; /* Check from the end back */
  		if (buf[index] != POISON) {
  			pr_err("poison value missing at index: %d\n", i);
  			goto fail;
  		}
  	}
  
  	return 0;
  fail:
  	failed_tests++;
  	return -1;
  }
  
  static void __init selftest(void)
  {
  	/*
  	 * tc() uses a destination buffer of size 6 and needs at
  	 * least 2 characters spare (one for null and one to check for
  	 * overflow).  This means we should only call tc() with
  	 * strings up to a maximum of 4 characters long and 'count'
  	 * should not exceed 4.  To test with longer strings increase
  	 * the buffer size in tc().
  	 */
  
  	/* tc(src, count, expected, chars, terminator, pad) */
  	KSTM_CHECK_ZERO(tc("a", 0, -E2BIG, 0, 0, 0));
  	KSTM_CHECK_ZERO(tc("", 0, -E2BIG, 0, 0, 0));
  
  	KSTM_CHECK_ZERO(tc("a", 1, -E2BIG, 0, 1, 0));
  	KSTM_CHECK_ZERO(tc("", 1, 0, 0, 1, 0));
  
  	KSTM_CHECK_ZERO(tc("ab", 2, -E2BIG, 1, 1, 0));
  	KSTM_CHECK_ZERO(tc("a", 2, 1, 1, 1, 0));
  	KSTM_CHECK_ZERO(tc("", 2, 0, 0, 1, 1));
  
  	KSTM_CHECK_ZERO(tc("abc", 3, -E2BIG, 2, 1, 0));
  	KSTM_CHECK_ZERO(tc("ab", 3, 2, 2, 1, 0));
  	KSTM_CHECK_ZERO(tc("a", 3, 1, 1, 1, 1));
  	KSTM_CHECK_ZERO(tc("", 3, 0, 0, 1, 2));
  
  	KSTM_CHECK_ZERO(tc("abcd", 4, -E2BIG, 3, 1, 0));
  	KSTM_CHECK_ZERO(tc("abc", 4, 3, 3, 1, 0));
  	KSTM_CHECK_ZERO(tc("ab", 4, 2, 2, 1, 1));
  	KSTM_CHECK_ZERO(tc("a", 4, 1, 1, 1, 2));
  	KSTM_CHECK_ZERO(tc("", 4, 0, 0, 1, 3));
  }
  
  KSTM_MODULE_LOADERS(test_strscpy);
  MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
  MODULE_LICENSE("GPL");
  